Color picture tube having an inline electron gun with asymmetric focusing lens

Abstract

A color picture tube includes a screen and an improved inline gun for generating and directing three inline electron beams along separate paths toward the screen. The improved electron gun has an asymmetric beam-forming region and an asymmetric main focus lens. The asymmetry of the main focus lens is matched with the asymmetry of the beam-forming region to focus substantially all portions of each of the beams at the screen.

What is claimed is: 
     
       1. In a color picture tube including a screen and an inline electron gun for generating and directing three inline electron beams along separate paths toward said screen, the improvement comprising said electron gun having an asymmetric beam-forming region including three inline cathodes and at least two electrodes, a first electrode and a second electrode respectively spaced from said cathodes, each electrode including three inline apertures therein which are substantially aligned with said cathodes, and wherein said first electrode includes a separate slot superposed on each of the apertures therein, each of said slots facing said second electrode and being elongated in a direction perpendicular to the inline direction of the apertures in said first electrode,   said electron gun having an asymmetric main focus lens, the asymmetry of said main focus lens being matched with the asymmetry of said beam-forming region to focus substantially all portions of each of said beams at said screen, said main focus lens including two focus electrodes, the facing portions of which each including a peripheral rim and three separate inline apertures therein set back from the rim, and said peripheral rims being elongated in the inline direction of said inline apertures and forming an asymmetric focus field, and   said electron gun including a prefocus lens between said beam-forming region and said main focus lens, said prefocus lens comprising three electrodes including two electrically connected side electrodes, one of which is common with one of said main focus lens electrodes, and a center electrode which is electrically connected to the other of said main focus lens electrodes that is not common to a prefocus lens electrode.   
     
     
       2. An inline electron gun for generating and directing three inline electron beams along separate paths, comprising six electrodes spaced from three inline cathodes, each electrode including at least three inline apertures for the passage of three electron beams therethrough, the third and fifth electrodes from said cathodes being electrically connected and the fourth and sixth electrodes from said cathodes being electrically connected and operable at an anode voltage,   the facing portions of the fifth and sixth electrodes from said cathodes each include a peripheral rim and three separate inline apertures therein set back from the rim, said peripheral rims being elongated in the inline direction of said inline apertures and forming an asymmetric focus field,   the first and second electrodes from said cathodes comprising a beam-forming region of said gun, and the beam-forming region including means for forming an asymmetric electrostatic lens along each of said electron beam paths, the asymmetry of said lenses being matched to the asymmetry of said focus field formed by the peripheral rims of the fifth and sixth electrodes.   
     
     
       3. The electron gun as defined in claim 2 wherein the asymmetric electrostatic lens of said beam-forming region is formed by said first electrode including a separate slot superposed on each of the apertures therein, each of said slots facing said second electrode and being elongated in a direction perpendicular to the inline direction of the apertures in said first electrode. 
     
     
       4. The electron gun as defined in claim 2 wherein the asymmetric electrostatic lens of said beam-forming region is formed by said second electrode including a separate slot superposed on each of the apertures therein, each of said slots facing said first electrode and being elongated in a direction parallel with the inline direction of the apertures in said second electrode. 
     
     
       5. An electron gun for generating at least one electron beam, comprising an asymmetric beam-forming region including a cathode and at least two electrodes each having at least one aperture therein, at least one of the beam-forming region electrodes including a slot superposed on an aperture therein for forming an asymmetric field,   a two electrode asymmetric main focusing lens, the asymmetry of said main focusing lens being matched to the asymmetry of said beam-forming region to focus substantially all portions of the electron beam at a common position relative to said electron gun, and   a three electrode prefocus lens located between said beam-forming region and said main focus lens wherein an electrode of said main focusing lens and said prefocus lens are common.   
     
     
       6. In a color picture tube including a screen and an inline electron gun for generating and directing three inline electron beams along separate paths toward said screen, the improvement comprising said electron gun having an asymmetric beam-forming region and an asymmetric main focus lens, the asymmetry of said main focus lens being matched with the asymmetry of said beam-forming region to focus substantially all portions of each of said beams at said screen,   said main focus lens being formed by two electrodes,   said electron gun including a three electrode prefocus lens between said beam-forming region and said main focus lens, and   said beam-forming region including three inline cathodes and at least two electrodes, a first electrode and a second electrode respectively spaced from said cathodes, each electrode including three inline apertures therein which are substantially aligned with said cathodes, and wherein said first electrode includes a separate slot superposed on each of the apertures therein, each of said slots facing said second electrode and being elongated in a direction perpendicular to the inline direction of the apertures in said first electrode.   
     
     
       7. The tube as defined in claim 6 wherein the facing portions of the two main focus lens electrodes each include a peripheral rim and three separate inline apertures therein set back from the rim, and said peripheral rims are elongated in the inline direction of said inline apertures and form an asymmetric focus field. 
     
     
       8. The tube as defined in claim 6 wherein the three electrode prefocus lens comprises two electrically connected side electrodes and a center electrode having different electrical connection means. 
     
     
       9. In a color picture tube including a screen and an inline electron gun for generating and directing three inline electron beams along separate paths toward said screen, the improvement comprising said electron gun having an asymmetric beam-forming region and an asymmetric main focus lens, the asymmetry of said main focus lens being matched with the asymmetry of said beam-forming region to focus substantially all portions of each of said beams at said screen,   said main focus lens being formed by two electrodes,   said electron gun including a three electrode prefocus lens between said beam-forming region and said main focus lens, and   said beam-forming region including three inline cathodes and at least two electrodes, a first electrode and a second electrode respectively spaced from said cathodes, each electrode including three inline apertures therein which are substantially aligned with said cathodes, and wherein said second electrode includes a separate slot superposed on each of the apertures therein, each of said slots facing said first electrode and being elongated in a direction parallel to the inline direction of the apertures in said second electrode.